Horgan has recovered from the knee ligament strain that kept him out for four weeks and is restored to the right wing in place of Andrew Trimble.
Trimble has a fractured finger and is expected to be sidelined for a week, forcing him to drop out of the squad for Saturday's showdown with the Georgians.
After such an abject opener, O'Sullivan was well within his rights to swing the axe in a bid to reignite the nation's hopes of reaching the quarter-finals.
But he has given his first-choice XV a chance to atone for the nightmare at the Stade Chaban-Delmas - a policy that he claims has worked in the past.
"I wasn't in the mood for slashing and burning because of a bad performance like that," he said.
"We're a better team than that. In the past when the players have come up short, I've backed them and given them a vote of confidence to get it right.
"And they've always repaid that vote of confidence. I didn't see the logic of changing that approach this time.
"If you create an environment where a player gets dumped after one bad performance, you don't build any confidence in the squad. We're trying to build confidence, not erode it.
"The players are aware it was a bad performance and they have a chance to fix it. We've had bad performances before and haven't reacted by making lots of changes.
"I've known most of the players for a number of years. They were very disappointed, upset and angry with what they delivered against Namibia. I want them to put it right.
"In 2002 we got 'hockeyed' at Twickenham and there were a lot of people thinking there should be a slash and burn job on selection.
"I told the players they're not as bad as that and they proved me right by beating Scotland handsomely. We've done this before."